Soft silicone hydrogel contact lenses are increasingly becoming popular because of their high oxygen permeability and comfort. But, a silicone hydrogel material typically has a surface, or at least some areas of its surface, which is hydrophobic (non-wettable) and susceptible to adsorbing lipids or proteins from the ocular environment and may adhere to the eye. Thus, a silicone hydrogel contact lens will generally require a surface modification.
Recently, a new cost-effective approach has been described in U.S. pat. Appl. pub. No. 2012/0026457 A1 for applying a non-silicone hydrogel coating onto a silicone hydrogel contact lens, in which an organic solvent-based coating solution of a polyanionic polymer is involved in forming an interpenetrating base coating (i.e., an anchoring layer) on a silicone hydrogel contact lens and then a partially-crosslinked hydrophilic polymeric material are covalently attached onto the anchoring layer directly in a lens package during autoclave. Silicone hydrogel contact lenses produced according to such an approach can have a water-gradient structural configuration and a soft and lubricious surface.
However, the resultant silicone hydrogel contact lenses may be susceptible to high deposition and accumulation of positively charged antimicrobials (e.g., polyhexamethylene biguanide, Polyquaternium-1®, or the like) commonly found in most multipurpose lens care solutions, due to the presence of the anchoring layer of a polyanionic material. Those positively charged antimicrobials adsorbed by the silicone hydrogel lenses may be released into the eye and may cause undesirable clinical symptoms in some persons, such as diffuse corneal staining and product intolerance, when the lenses are worn by patients.
Therefore, there is still a need for a method for producing silicone hydrogel contact lenses with a durable non-silicone hydrogel coating which has a minimized susceptibility to high deposition and accumulation of positively charged antimicrobials. There is also a need for silicone hydrogel contact lenses with such a durable coating thereon.